This is a guest post by Melissa Marquez.
With summer inching closer every day, one way to find relief from the Australian heat is to take a dip at one of Australia’s famous beaches or rivers. What you probably aren’t thinking about is that you’re sharing the water with one of the world’s oldest animals: the shark.
Worldwide, there are about 500 species of sharks. Of these, about 180 species live in Australian waters. Well-known species include the great white shark (Carcharodon carcharias), the grey nurse shark (Carcharias taurus) and the bronze whaler (Carcharhinus brachyurus), but the greater public often forget that sharks aren’t uniformly grey, robust, or in possession of sharp teeth. These less famous sharks are often overlooked, both by the community and by scientists.
One can be seen if you find yourself on the western coast of Australia and stop by Ningaloo Coast. If you're lucky, you might spot a well-known gentle giant: a whale shark (Rhincodon typus), more than seven metres long, discernible by its unique arrangement of light and dark patterning. As the world’s largest living fish, they are highly migratory and often appear in large filter feeding groups. If you manage to snap a picture of an individual, you can send it over to Wildbook for Whale Sharks, where it will become part of a database of whale shark records that dates back to 1995.
Some sharks don’t make such a grand entrance as the massive whale shark; they instead hide in plain sight through camouflage. Sharing the waters are the elusive tasselled wobbegong sharks (Eucrossorhinus dasypogon), which can reach up to four metres in length. What sets these sharks apart is that they’re flattened and ornately patterned to blend in with the seafloor. The word ‘wobbegong’ is thought to come from an Aboriginal word meaning ‘shaggy beard,’ pointing to the growths around their mouth that act as sensory barbs. This bottom-dweller takes advantage of its camouflage by ambushing unsuspecting fish and invertebrates.
Another funky-looking water resident is the green sawfish (Pristis zijsron), a ray with a shark-like body and an elongated snout that bears pairs of teeth that resemble a chainsaw. They are greenish brown in colour and can reach up to four metres in length. Sawfish are most commonly found along the coast of Queensland, the Northern Territory and Western Australia. Little is known about their populations and they are listed as Vulnerable by the International Union for Conservation of Nature and Natural Resources (IUCN).
Think you can escape sharks by skipping the ocean and opting for a river dip instead? Think again! Some sharks, like the speartooth shark (Glyphis glyphis), inhabit freshwater. These sharks tend to look like your ‘typical shark,’ and are grey in colour with a white underbelly, reaching up to two metres in length. Speartooth sharks have only been found in a few locations along the Northern Territory and Queensland, and very little is known about them.
If you can catch a flight to Sydney, sneak a peek into the waters and you’ll possibly see a Port Jackson shark (Heterodontus portusjacksoni), affectionately known as the PJ shark. Measuring up to one and a half metres long, it has a distinctive harness-like pattern across its shoulders, ridges above its eyes, and a pig-like snout, and lay spiralled eggs that sometimes wash ashore once the shark pups are born. This species can also be found in Victorian waters and many other areas off the Australian coast.
While in Sydney, you may also spot a brilliantly spotted shark known as the zebra shark (Stegostoma fasciatum), named for their black and white stripes on juveniles which morph into spots as they mature. These reef inhabitants can reach up to two and a half metres in length and are usually seen resting on the seafloor.
Speaking of stripes, the tiger shark (Galeocerdo cuvier) is also an Australian resident. This shark can reach up to six metres in length and can be seen from shallow reefs to the open ocean. Known as the ‘garbage cans of the sea,’ this scavenger has had some pretty weird stuff found in its stomach: TNT, chicken wire, a suit of armour, and a porcupine, to name a few!
Unfortunately, these magnificent animals often get a bad rap, and whilst some are dangerous, it is important not to ignite hysteria when it comes to sharing the waters with our shark neighbours. Smart drum lines, nets to protect beaches and other warning systems are all being used to manage sharks and their interactions with humans. However, these interventions may cause problems for other marine life.
Instead, an increase in shark-spotting initiatives and other non-lethal ways to alert beachgoers when sharks are in the area could be used to help raise awareness and appreciation of these mysterious marine creatures. Perhaps by educating the public about these diverse sharks, we can better share and protect their habitats into the future.